Understand your point, though doesn’t match my experiences turning a iPhone off fully charged before sleeping (including configuration you mentioned) — and then leaving it off for the night only to find the battery drained significantly in the morning upon turning it on. Beyond that, unlike the OP article that’s subject of this thread, not aware of any Apple support article that clearly states off is off if XYZ is done. Obvious solution would be a switch that physically disconnects the battery, drains capacitors, etc. — though it would likely require redesign of how the system clock pulls power, though might be wrong:

- https://apple.stackexchange.com/questions/87580/how-does-an-...